1. Field of the Invention
The invention relates to an image sensor having an improved package structure, and in particular to an image sensor that has a firm package structure and may be manufactured more conveniently.
2. Description of the Related Art
A general sensor is used to sense signals, which may be optical or audio signals. The sensor of the invention is used to receive image signals or optical signals. After receiving the image signals, the sensor converts the image signals into electrical signals, which are then transmitted to a printed circuit board via a substrate.
Referring to FIG. 1, a conventional image sensor includes a substrate 10, a frame layer 18, a photosensitive chip 26, a plurality of wires 28, and a transparent layer 34. The substrate 10 has an upper surface 12 on which first terminals 15 are formed, and a lower surface 14 on which second terminals 16 are formed. The frame layer 18 has a first surface 20 and a second surface 22 adhered to the upper surface 12 of the substrate 10 to form a cavity 24 together with the substrate 10. The photosensitive chip 26 is arranged within the cavity 24 and is mounted to the upper surface 12 of the substrate 10. Each wire 28 has a first terminal 30 and a second terminal 32. The first terminals 30 are electrically connected to the photosensitive chip 26, and the second terminals 32 are electrically connected to the first terninals 15 of the substrate 10. The transparent layer 34 is adhered to the first surface 20 of the frame layer 18.
As shown in FIG. 2, the first terminals 15 of the substrate 10 project over the upper surface 12 of the substrate 10, and a gap 29 is left between two adjacent first terminals 15. Therefore, when the frame layer 18 is adhered to the substrate by an adhesive, the product will be contaminated if the adhesive is not well controlled and flows out from the gaps. Furthermore, because of the gaps 29, the frame layer 18 may not be firmly adhered to the substrate 10 and may be easily damaged.
An object of the invention is to provide an image sensor having an improved package structure and improved product quality.
To achieve the above-mentioned object, the invention provides an image sensor including a substrate, a coating layer, a frame layer, a photosensitive chip, multiple wires, and a transparent layer. The substrate has an upper surface formed with first terminals projecting over the upper surface, and a lower surface formed with second terminals. The coating layer is applied to the upper surface to fill between any two adjacent first terminals and to flatten the first terminals. The frame layer is adhered to the coating layer so as to form a cavity together with the substrate. The photosensitive chip has bonding pads and is mounted to the upper surface and within the cavity. The wires electrically connect the bonding pads to the first terminals, respectively. The transparent layer is arranged on the frame layer to cover the photosensitive chip so that the photosensitive chip may receive optical signals passing through the transparent layer.